Process and apparatus for separating finely-divided materials.



W. A. SCHMIDT.

PROCESS AND APPARATUS FOR SEPARAHNG HNELY DIVIDED MATERIALS. APPLlCATIONnuzn OCT. w. 1916.

1,298,409. Patented Mar. 25,1919.

imam/0r. h/rer A, deb/MM? Wm M Ava Amr/re 45 l action successively indlfi'erent parts offthe app ratus, under n rensan t na b se so obtainingalkali meta-1,

UNITED STATESPATENT OFFICE.

WALTER A. scanner, I408 ANGELES, CALIFOiNIA; ASBIGNO B '1'0INTEBNLTIOIfA-L rnncxrrranorr conrm, or

roams;

L05 ANGELEQCALII O BNIA, A GOBPOBA'IIOR OF CALI-- "PROCESS AND APP QBATUS FOB SEPLRATING FINEiT-DIVIDED MATERIALS.

Specification 01' Letters Patent. Patented Mar. 25, 1919.

Application filed came: 17, 1818. 8 erialllo.128,080.

citizen of the United States, residing at Lee wholly by electricalaction, for an apprecia;

ble portion-of the finer particles to be pro;

particles dust or fume.

Angeles, in the county of Los Angeles and State of California, haveinvented a new and useful Process and Apparatus for SeparatingFinely-DividedMaterials, of which the following is a specification.

This invention relates particularly to a process and apparatus forselectively separating from a gas, particles of different size orofdilferent material suspended therein such gas being for example theeffluent o kilns or furnaces containing dust or fume. The invention alsoprovides for separation of particles of difl'erent degrees of finenesswhich are present in a state of mixture, and which it is desirable toseparate or selectively recover according to slze or fineness. I

The main object of the present invention is to selectively collect orseparate the particles of difi'erent degrees of fineness in such mannerthat both the coarser and the finer particles are effectivelyprecipitated. For collection or precipitation of comparatively coarsearticles, mechanical separators, such as sett ing chambers orcentrifugal separators, are efi'ective, but they are not effective inthe precipitation or collection of very fine My present inventionprovides for collection or precipitation of the coarser articles by suchmechanical action, followed by the action of more efiicientprecipitating means, namely,the action 0 an electric field, which iscapable of precipitatg the finest particles, with comparative rapidity.7

On account of the extreme rapidity and efliciency of'electricprecipitation there is a tendency, when the precipitation is effectedcipitated along with the coarser. e bout :th wpre pwm c rame thong I yam ng..o g p aa pi atmg trviprecipitation ,or separation ca 1,200,881foe. 10.191 ic case 10 much however, as the mechanical precipitw o n, whther by st as ar rs fl i i I p ugal actio is quite afis ivaqilma ji fiition of particles of terial and almost ineifective on very fine dust,the two stage precipitation with initial action by mechanicalprecipitation, followed by electrical precipitation, gives a cleanerseparation than is otherwise possible, the coarser material being almostwholly reclpitated by mechanical action and the er dust being almostwholly precipitated by the electrical action.

It will be understood that in'case there are present in the Suspendedmaterial particles which are of a fiocculent or porous nature, they willpossess a buoyancy comparable to that of smaller com act particles, sothat the process is applica 1e enerally to separaifl'erent buoyancy,whether such buoyancy be due to the relatively small size of theparticles or to rela tively small density thereof.

This process ishereafter described as applied in connection with arotary kiln for burning cement mix containin a small pro- Figure 1 is asideelevation partly in seei tion of one form of such apparatus.

Fig. 2- is a transverse section on line 2-2, in Fig. 1. p

Fig. 3-,- 1s a. artly sectional elevation of another form 0 theapparatus. 7 i

Fig 4- is a section on line 4-4.-

Fig. 3. Referring to Figs. 1 and 2, the apparatus therein sliqwn is Edated for. use in connec tion "with a; cement ,urniiig'lriln, indicated"of tlie usual"rotagr" type provided with 1 V 21 at ts, lower and:ccnnuunieatm -at=1ts 4, "a condu il'fo r;eloiigated chamber' 5 extends;

H603 gang: 10o

trical pre'cipitator indicated at 6. Said chamber operates as a coolingchamber and also as a mechanical recipitatin means or chamber an isrovid at its 6 bottom with hoppers or bins in which the material settlesor accumulates, 'said hop or bins bein provided with means, sue as.gates 8, for rawing ofl material therefrom. he cross sectional area ofthis conduit or chamber 5, ispreferabl considerably in excess of that ofthe interior of the rotary kiln 1, so that the will pass through saidconduit or chain r with sufliciently low veloc ity to enable thecoarserparticles carried thereby or suspended therein to settle out orprecipltate by the action of gravity. The electrical precipitator 6, maybe of any suitablet pe, comprising, for example, the lower hea er 9 intowhich the conduit 5 opens; an upper header 10; vertical pipes or flues11, connecting said upper and lower headers and constituting collectinelectrodes; and discharge electrodes 12, ormed for example as wires,extending axially in 25 the respective pipes or flues 11, and hung froman ins lated support 13. Said insulated support 13 maybe connected bywire 14 to rectifier 15, having supply connections 16 andl7 to a hi htension alternatin 'cirlso a groun connection 18, and thecollecting'electrodes 11 of the precipitator being also grounded asindicated at 20, to complete the electric circuit connection. The upperheader 10 may comcuit, said rectifier aving a 85 municate with a stackor other means for cleaned gas. Bins or carrying away the 21, areprovided at the dust receiving means bottom of lower header. 9 and areprovi I with means 22 for removing or discharging My p is carried out inconnection with the burning of a Portland cement mixgure in the abovedescribed apparatus as folows:

Inthe operation of the rotary kiln 1,'the gases passi theref tain aconsi rable quantitfy of dust. When the silicious constituent oblthecement mix; ture contains an apprecia e percen o potassium, the effectof the heat in th e dlinkering operation causes -volatilization of alare portion rived from suchconstituent, and an impor- "tant object of thepresent invention in such 5 casesis to obtain a (product containing suchpotassium compoun to render it commercially valuab e. In the regularoperation of the apparatus the dam- Ear 4 is closed and the gases commfrom the in are forced to pass by nature draft or otherwise th o g theconduit or chamber l5 and the precipitator 6, wherein they 'are cooledmore or less, so that during the time a the traverse theapparatus andhetero they are dis harged therefrom, the volathe mixture is whollshaken ofi from time to timeded the dust continuously or from time totime.

rom into the stackB eonof compound, de-' in suficient roportion poundderived from or large]; can a so as to form a clou of'suspen edparticles in the gas. The alsocontains a consid- "erable quantity 0other solid particles or dust, mechanically blown outof the kiln, whichare, however, in ne'ral, much coarser or larger in size than t particlesresulting from condensation of the, potassium compound. These coarser orlarger particles settle to a large extent in passing through the conduitchamber 5 and are collected in the b ns 7, from which the may bewithdrawn, either continuously or ram time to time, by suitable means,and may be returned to the kiln or otherwise utilized. The gas passingfrom the conduit 5 to the electrical precipitator 6 contains only veryfinely divided material consisting largel of potassium compound and alsoincl in the finer particles of dusth lr l)owfi cilver m the kg, and mpassmgt ug t e precipitator, is is subjected to electrical action bmainta mg a high ntial difierence tween the discharge ectrodes 12, andthe collecting electrodes 11, by operation of the in tension directcurrent supplied through t e rectifier, from the alternating currentsupply circuit. The fine particl including the potassium compound, are e'ted on the 95. collecting electrodesll, and,i ,are

by suitable means, not shown, and collected in the bins 21 at the bottomof the lower header 9, from which the collected material may beremoved,either continuously or from time to .time. This collected materialcontains an amount of potassium compound which 'is tilized potassium com-many times that. contained in the product collected in the mechanicalas r bins 7. Myprocessmayalsobea 'edinconnectron with centrifugalseparation, and in that case, the ratus shown in Figs. 8 and 4 may beuse the f1 23for supplyingthe dust carrying gas toe cyclone dustseparatorQQwhoseoutetQfiisconnectedtd header 9 of the electricgzecipitator 6.

dustc gasmay 'drawntromauy furnace, or other apparatus producing dust ofdili'erent' degrees of fin eness. In this case'the operation of thecyclone dust separator causes the heavier and larger par-. unclessuspended in the gas to he collected mthe bin or hopper 28 thereof,while the finer particles containing for examglr'the potassium(mentioned a re in connection wit the application of the procass to acementjkilmlare on to'the' electrical precipitator 6, wherein they areprecip tated.

An important application of my invention, as illustrated in Fig. 8, isin connection I with grinding or mills for-the urpose of removing theline y ground ma "al I no lower 26, which discharges into the lower I ffrom the coarser material in the'mill so as -to maintain 'fullefliciency of the mill in mg action in cyclone separator 24 (or in agravitative settling chamber, if desired) and the gas is then passedthrou h the electrical precipitator to collect the er material or dust.The coarser and liner particles being separately collected in thismanner, may be separately utilized, or if only the finer lperodnot isdesired, the coarser product may returned for regrinding. With thisoperation, none of the finely ground material or dust drawn olf from themill by the air current, is returned to the mill so that the cushioningor clogging eflect due .to dust in the mill and interfering withefi'ective grindirfliig is Wholly eliminated, and maximum e ciency ofgrinding is maintained.

piles, tailings or the 1's, the solid tions as above described.

The process as above described is applicable in connection with therecovery of an alkali metal compound from a silicate roc in connectionwith a cement process, or any other case where lime is present, so as toliberate the potassium compound or other alkali metal compound. Theprocess is also applicable for separation of ore constituents, passingoff as dust and fume from smelters and the like, the coarser particlesbeing caught 'by the mechanical separator, and the finer particles orfume being collected b the electrical precipitating action. In su'ccases, as well as in "the case of cement dust, the selection as to sizeefiec'ted by this process may also result in a' selective separation asto chemical constitution, particularly in cases where the fumeprecipitated by the electrical action results from condensation ofmetallic or other vapors passing over with the coarser dust, in thesmelter fluegases.

The above described process ofselective separation may also be appliedin any case w ere particles of different size or density ndcd in a gas,and it may even be 'applie with advantage to the separation ofconstituents of difl'erent fineness or density, contained in such ascuflan a cles of such aglgregates being brough into suspension in t egas in an suitable manner an the gas being then an jected to Successivemechanical and electrical separating ac- In some cases, there mayadiiference in density of the particles, resulting in a are S differencein buoyancy, and in such cases, the less buoyant particles are caused tosettle by gravit n the settling chamber or otherwise mec anicallyseparated as above described and the more buoyant articles are carriedthrough the mechanica separators and precipitated by electrical action.

The term mechanical separation or mechanical precipitation, as hereinused, applies to any operation in which dust is separated orprecipitated by the action of gravity, centrlfuga force or othernon-electrical force, and the term electrical precipitation applies toany operation in which dust is separated or precipitated by the actionof an electrica tween electrodes by the production at such electrodes ofa high potential difl'ercnce, either direct or alternating and eithercontinuous or intermittent.

What I claim is:

'1. The process of selectively se arating and collecting materialsuspended in a gas which consists in causin a stream of such gas to flowat such ve ocity that coarser particles are separated therefrom by themechanical action of a force dependent on the mass. of the particles,and then subjecting said gas current, containing the rewhich consists incausing a stream of such gas to move in an unobstructed flow at suchvelocity that coarser particles are separated therefrom b the mechanicalaction of a force depen out on the mass of the particles, and thensubjecting said s current, containing the remaining artic es, incontinued flow to the action 0 an electric field to precipitate thefinerseparticles therefrom.

3. An apggratus for ectively separatiizfi materials m a current of gasin whi they are suspended comprising a settling chamber, means forpassing the gases through the settling chamber. at such velocity thatthe coarser articles carried thereby will settle by gravity in saidchamher, a continuous-flow electrical precipita-tor connected to receivethe gas from said settling chamber and adapted to precipitate the finerparticles therefrom, and an exit flue from said preci itator.

4. An ap aratus or selectively separatin materials in a current of gasin w 'c they are sus ded com rising a settling chamber having an unructed passage therethrough, means for passing the gases through thesettling chamber at such velocity that the coarser particles carriedthereby will settle by gravity in said chamher, a continuous flowelectrical precipitator connected to receive the gas from said settlingchamber and adapted to precipitate the finer particles therefrom, and anexit flue from said precipitator.

5 An apparatus con-uprising a furnace, a settling cham'ber connected tothe exit of said furnace, means for passing the exit gases through thesettling chamber at such velocity that the coarser particles carried bythe gas will settle by gravity in said chamher, a continuous-flowelectrical precipitator connected to receive the gas from said settlingchamber and adapted to precipitate the finer particles therefrom, and anexit flue from said precipitator.

6. An apparatus comprising a furnace, a

settling chamber having an unobstructed passage therethrough connectedto the exit of said furnace, means for passing the exit gases throughthe settling chamber at such velocity that the coarser particles carriedbly the gas will settle by gravity in said c iamber, a continuous-flowelectrical precipitator connected to receive the as from said settlingchamber and adaptet to precipitate the finer particles an exit flue fromsaid preci )itator.

1n testimon whereof I have hereunto set my hand, at 10s Angeles,California, this 9t 1 day of October, 1916.

WALTER A. SCHMIDT.

therefro n, and f It is hereby certified that in Letters Patent No.1,298,409, granted March 25, 1919, upon the application of Walter A.Schmidt, of Los Angeles, California, for

1 an improvement in "Processes and Apparatus for SeparatingFinely-Divided on in Letters Patent No. 1,298 409.

. Materials, an error appears in the printed specification requiringcorrection as follows: Page 3, line 78, after the word force" insert thewords dependent on the mass of the particles; and that the said LettersPatent should be read with this correction therein that the same mayconform to the record of the casein the Patent Office.

Signed and sealed this 11th day of November, A. D., 1919.

[snub] M. H. COULSTON,

Acting Commissioner of Patents.

Correct

